fix mysql 5.6.0 issue when dumping from older server releases
conditionally insert --set-gtid-purged=OFF option only when mysqldump version is >= 5.6.x
convert Dbmanager.execute methods to use backticks instead of system calls
remove temporary method #get_mysqldump_version
remove STDOUT ouput from tests
replace #stub! with #stub
remove #bundle from Mysql::Loader
fix failing spec